Polyurethane resins have excellent stretching properties. These resins thus have been widely used in materials for elastomers such as paints, coating agents, sealing materials, adhesives, fiber processing agents, artificial or synthetic leathers, and rolls, and fiber products. A need exists in these applications for improvement in heat resistance of polyurethane resins without sacrificing their stretching properties (residual strain and elongation), in order to prevent deterioration due to the thermal history in manufacturing or processing a final product from a polyurethane resin, or in order to provide a final product with improved durability.
Non Patent Literature 1, for example, discloses a method of adjusting the urethane group concentration and/or the urea group concentration of a polyurethane resin in order to improve the heat resistance.